fix: correct fog of war coordinate system (Y vs Z axis mismatch)

[braedonsaunders]

The fog of war was broken on some maps (100% coverage) and inverted on others (moving south revealed north) due to coordinate system mismatches:

1. VisionSystem used transform.y (altitude) instead of transform.z (depth) when calculating vision grid cells
2. CPU texture path had an inconsistent Y-flip that didn't match GPU path or shader expectations
3. Map dimensions weren't being passed to the fog shader, causing hardcoded 256x256 to mismatch actual map sizes (e.g., 320x320)

Changes:

• VisionSystem.ts: Use transform.z for all vision calculations
• FogOfWar.ts: Remove Y-flip in CPU path to match GPU/shader
• EffectPasses.ts: Add setMapDimensions() for dynamic map sizing
• PostProcessing.ts: Use setMapDimensions() with cell size
• VisionCompute.ts: Rename worldY→worldZ for clarity
• BuildingRenderer.ts, UnitRenderer.ts: Use transform.z for checks
• Minimap.tsx: Use transform.z for position and vision checks

https://claude.ai/code/session_013Hqn3PxBW8h7hpMNMKKv1e